Study On The Effect Of SNORA71B In Breast Cancer Brain Metastasis

Background:Breast cancer is the most common cancer in women patients and develop to brain metastases,further severely impairs patients' quality of life.No effective treatments for breast cancer brain metastasis are currently available.Penetration of the blood brain barrier is one of the breakthroughs for effective therapy of BM,and the effective treating substances across this physiologic barrier,or regulation molecule inhibit tumor cells crossing the BBB is still unknown.The underlying mechanism of BC cells across the BBB are also not well understood.snoRNAs are a class of small non-coding RNA molecules(60-300nt)widely presenting in the nucleolus of eukaryotic cell.With the development of second-generation sequencing technology,more data indicate that snoRNAs are abnormally regulated in tumors.However,the role of snoRNAs participating BCBM has not still been reported.Objective:We explored the function of SNORA71 B involving breast cancer metastasis to brain following function assay in different metastatic cells and an in vitro blood-brain barrier model.Then It will provide a theoretical basis for the follow-up targeted therapy of breast cancer brain metastasis.Methods:1.We first utilized GEO and SNORic database to analyze the expression of snoRNAs in different metastatic breast cancer tissues,and we screened SNORA71 B.2.The level of SNORA71 B expression was measured by reverse transcription and real-time PCR.3.We transfected the cell lines MDA-MB-231 and MDA-MB-231 BM with over-expression and knock down SNORA71 B,respectively.And the effects of SNORA71 B on cell ability of proliferation,migration and invasion were detected with CCK8 assay and Transwell.4.We performed western blotting assay to examine levels of marker molecules about EMT in SNORA71 B transfected MDA-MB-231 cells.5.Finally,an in vitro BBB model was utilized to estimate invasion ability of siSNORA71 Bs infected MDA-MB-231 BM cells by transwall.Results:1.SNORA71 B is significantly different expression related with metastasis in database of BCBM,and we found that the expression of SNORA71 B was significantly different and higher in BMBC tissues compared with BC tissues.Meantime,compared to normal tissues,the expression of SNORA71 B was also significantly different and higher in different metastatic ability BC cells.2.The results showed the expression levels of SNORA71 B was decreased in siSNORA71 Bs infected MDA-MB-231 BM cells,and expression of SNORA71 B was increased in SNORA71 B transfected MDA-MB-231 cells.The SNORA71 B promoted proliferation of different metastatic ability BC cells.3.The results showed SNORA71 B knock down repressed the migration capacity of high MDA-MB-231 BM cells.And the up-regulation of SNORA71 B promoted migration ability in MDA-MB-231 cells.The SNORA71 B promoted migration of different metastatic ability BC cells.4.The results indicated that the invasion of high MDA-MB-231 BM cells infected with siSNORA71 Bs was inhibited.Meantime,the over-expression of SNORA71 B promoted invasion in low BM MDA-MB-231 cells.The SNORA71 B promoted invasion of different metastatic capacity BC cells.5.As result shown that the level of E-cadherin was significantly decreased,and Vimentin was increased in SNORA71 B transfected low BMBC cells.The SNORA71 B promoted EMT,resulting BC cells transition and spreading.6.Fluorescence representative figures showed SNORA71 B knock-down exhibited lower green fluorescence in high MDA-MB-231 BM cells,indicating that fewer cells passed the BBB in siSNORA71 B infected high MDA-MB-231 BM cells.The SNORA71 B promoted the high BMBC cells across BBB in vitro,indicating SNORA71 B was important for brain metastasis.Conclusions:In conclusion,SNORA71 B promoted proliferation,migration,invasion and even EMT progress as well as high BMBC cells across the BBB.Our study indicated that increasing of SNORA71 B expression promoted BCBM through effecting function role and inducing EMT progress,and further promoted BMBC cells crossing the BBB.SNORA71 B may be a therapeutic target to treat BCBM in future.